Treatment of vacuum devices to remove occluded gases therefrom



'e. 1 1927. v F b H. c. RENTSCHLER TREATMENT OF VACUUM DEVICES TO REMOVE QCCLUDED GASES THEREFRO" I filed Sept. 20, 1924 INVENTbR HARVEY C. RENTSCHLER Patented Feb. 1, 1927.

UNITED STATESIPATENT OFFICE.

HARVEY CLAYTON EENTSCHLEB, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE COMPANY, A CORPORATION OF PENNSYLVANIA.

TREATMENT OF VACUUM DEVIGEQ TO REMOVE OCCLUDED GASES THIEREIFROIM.

Application filed September 20, 1924. Serial No. 738,742.

This invention relates to the manufacture of high potential discharge devices and more particularly to a method of exhausting high voltage apparatus such as X-ray tubes and other discharge devices to remove the occluded gases from the walls of the envelope and from the leading-inwires and electrodes sealed therein.

This application is acontinuatlon in part May 11 1922. I v

In exhausting vacuum devices such as X- ray tubes, radio tubes and the like, which arc to be operated by high voltages, difiiculty 15 has been encountered heretofore, in removing the occluded gasesfrom the leading-1n wires and the electrodes and from the walls.

- of the envelope so that, when the apparatus is put in operation, gases will not be evolved which will impair the vacuum and seriously affect the operation of the device.

The portions of the-leading-in wires lylng immedlately adjacent the glass press are particularlydifiicult to treat since if these wires are heated sufficiently to drive the gases therefrom, where they are contlguous p to the press, they will be over-heated at points removed from the press, with deleterious efiectsto the wire. Moreover, the high temperature to which it is necessary to heat the wire adj'acent'the press, in order to remove the. gases therefrom, often results in cracked presses. The-usual method of treating the electrodes and the leading-in'conductors for X- ray tubes and similar devices consists in subjecting the metal parts to a h1gh voltage, re'ct current or low frequency discharge during the evacuation of the envelope or con- 40 tainer. This discharge results in heating the electrodes and'parts of'the leading-in conductors near the center of the device to a greater extent thanthose parts of the leading-in Wires adjacent the press since the 4 press conducts the heat away from the portions pf the leading-in wires adjacent thereto at a greater rate'than the heat is radiated from those parts of theleading-in wires.

more remote from the press. It will be understood, therefore, that by this method, the

leading-in wires are not sufficiently treated in the vicinity ofthe press and these untreated parts, when the apparatus is later operated, will give ofi gases or vapors which .55 will impair the operation of the apparatus.

. of the device and condenses on another part.

'.from the envelope which seriously impair :the vacuum. This appears to be true regard- 10 of my application Serial 'No. 562,003 filed" less of the extent to which the electrodes are heated during exhaustion and is probably due to the fact that there is a quantity of cpndensible gases in the envelope which by slmpleheating, is' driven 01f from one part In the operation of the device when the electrodes are subjected to a high voltage, the strong electric field produced thereby, probably pulls this gas or vapor olf from the parts: of the envelope or electrodes on which 7 it has condensed by means of electric stresses or similar action.

One of the'objects of this invention is to provide a method for effectively removing the occluded gases from the glass and metal arts of a vacuum device.

Another object is to provide a method of removing occluded -gases or other impuris ties from the leading-in wires and electrodes of an X-ray tube or similar device.

Another object is to provide a-method of treating high voltage discharge devices during evacuation to completely remove the condensible gases therefrom.

Other objects and advantages will hereinafter appear.

"parts and it ispossible to sub'ect the glass parts to a thorough treatment y connecting one terminal of the high frequency source to the outside of the glass envelope and connecting one of the electrodes of the tube to the other terminal. The tube should also be heated in the usualmanner of exhausting in addition to this high frequency treatment.

The high potential, high frequency cur-'3" rent may also be connected directly to the electrodes of the device and when so con- 'nected,causes a vigorous sparking discharge therebetween and especially between those and that the same method of exhaustion is portions of the leading-in wires immediately adjacent the press since, as is well under-- stood, such a discharge tends to take the longest path possible through the residual This high frequency discharge in addition to heating the various parts creates an electrostatic tield which pulls the occluded or closely adherent gases or vapors and other impurities from the leading-in wires and from the electrodes and permits them to be removed in the usual manner by the pump.

In order that the invention may be more fully understood, reference may be had to the accompanying drawing showing diagrammatically, a high frequency, high volt-- age source associated with'an X-ray tube in such manner as to permit the tube to be subjected to an exhaust treatment in accordance with this invention.

While the invention is shown in connection with the exhaustion of X-ray tubes, it is to be understood that it is not so limited applicable to radio tubes and other forms of vacuum discharge apparatus.

The drawing shows somewhat diagrammatically, an X-ray tube having an envelope 1, containing a cathode 2 and an anode 3 provided respectively with leading-in conductors 4. and 5 which extend through the oppo' site ends of the tubular extensions 6 and 7 of the envelope. The envelope 1 is connected to an exhausting system 8 in any suitable manner as by the exhaust tube 9.

Any suitable apparatus may be provided for supplying high voltage, high frequency current to the device to be treated. By Way of example of such apparatus, one terminalof the secondary of a Tesla coil 11 may be connected to the leading-in wire 4 of the tube and the other terminal may be connected to the outside of the envelope by means of a metal collar 12 or other suitable connection.

As a desirable means for impressing high frequency current on the primary winding 13 of the Tesla coil, I have shown an alternating current generator 14 for supplying current to the primary winding 15 of a transformer 16 which steps up the voltage.

. The secondary 17 of transformer 16 has one of its terminals connected to one end of the primary coil 1?- and has the other terminal connected, through a suitable spark gap 18, to the other end of the primary coil 13. A capacity 19 is provided in the circuit for a purpose which will hereinafter appear.

High frequency current set up in the primary coil 13 is stepped up by the adjustable secondary 10 from which it is conducted to the tube by the conductors 20 and 21. It will be readily understood that a resonant or oscillating circuit is formed by the condenser 19 and the primary winding 13 and that by rapidly discharging across the spark gap 18, high frequency oscillations are set up in the circuit and these oscillations stepped up by the secondary winding 10 or the Tesla coil.

In the operation of treating the tube by means of the high potential, high frequency current so developed, the tube is first exhaustedin the-usual manner by the exhaust system 8 to the desireddegree. A discharge envelope and from the electrodes and permit them to be removed by the pumping, system 8.

The conductor 20 may then be disconnected from the leading-in wire 4 and joined to the leading-in wire 5 and a discharge passed between the anode 3 and thewall of the envelope to remove the gases from this electrode and leading-in wire associated therewith. If desired, the terminals of the secondary of the Tesla coil may be connected to both leading-in wires and a discharge passed directly between the electrodes 2 and 3. This discharge will heat the electrodes and the leading-in wires, particularly those portions of the leading-in wires immediately adjacent the press by virtue of the tendency of said discharge to take the longest gas path in the tube.

It is to be understood that the invention is not limited to exact: circuit connections shown, but said connections may be reversed or be otherwise suitably arranged and various means may be provided for connecting the high frequency source to different parts of the envelope.

According to this invention, the treating of the electrodes takes place after the best possible vacuum obtained by the pump is obtained while the bulb is still on the pump, whereas in former processes, the discharge within the tube occurred during exhaustion and before the linal vacuum was obtained. The former method caused considerable sputtering of the electrodes which resulted in the formatiouot a deposit. of metal on the press and thus afforded opportunities for short circuits to occur. Also, in the processes heretofore used, the voltage which it was possible'to impress on the tube, was limited inasmuch as the low frequency or direct current, high voltage discharge had a tendency to puncture the envelope. With This discharge mavthe high frequency treatment given in accordance with this invention, very high potentials may be used without apparently having any bad effect-upon the press or upon the other parts of the device.

While I have illustrated what I new consider the preferred form of my invention, itis to be understood that the same is merely illustrative and that many changes may be made therein without departing from this invention.

What is claimed is: v

'1. The method of removing occluded gases from the glass and metal partsof a vacuum electric device which comprises passing a high frequency, high voltage discharge between the metal and glassparts of the device to createan electrostatic field therebetween.

2. The method of removing occluded gases from the vitreous envelope and metal parts of a 'vacuum electric device which comprises positioning an electrode adjacent the exterior surface of the envelope and passing a high frequency discharge between said electrode and the metal parts of the device.

3. The method of removin occluded gases from the glass parts and t e leadingm wires and electrodes of an evacuated discharge device which consists in disposing an electrode adjacent the external surface of the envelope and creating a high frequency, high v0 tage discharge between said external electrode and the leading-in wires and electrodes .of the device and eliminating the gases liberated by such discharge from the device.

4. The method of removing occluded gases from the glass and metal parts of a vacuum discharge device comprising exhausting the device by a suitable pumping means until a high vacuum is obtained therein, applying high frequency, high voltage power between said metal parts and said glass parts to drive out the occluded gases therefrom and further exhaustin the device 1% remove the gases which have %een driven o In testimony whereof, I have hereunto subscribed my name this 19th dayof September 1924. HARVEY CLAYTON RENTSCHLER. 

